Some Case Histories of Pile Foundations in Permafrost

by Duane Miller Miller, P.E., (M.ASCE),

Abstract: Foundations for permafrost conditions should conform to one of three basic design principles: keep it frozen, let it thaw, or thaw the ground before construction. To keep the permafrost frozen, the designer should minimize the heat flow into the frozen ground and should provide cooling to compensate for whatever heat load cannot be avoided. Elevating the structure above ground to isolate the building's heat from the frozen ground, to shade the ground during the summer, and to allow cold winter air to circulate under the building is one of the oldest methods of keeping the permafrost frozen. Once construction equipment was developed to place vertical structural elements in the ground efficiently, pile foundations became the common means of elevating structures abovegrade. Piles in permafrost need to resist the sustained and short-term loads imposed by the structure as well as the frost-heave load caused by the annual freezing of the activelayer. If the permafrost is degrading and thaw is unstable, the melting soil settles, and the pile also needs to resist the downdrag load of the settling soil.